Formation of oriented silver telluride on single and polycrystalline Ag films

Abstract

The formation, structure and morphology of silver telluride developed by the reaction of both (0 0 1) single or polycrystalline Ag films with subsequently vacuum deposited Te was investigated. Silver films 30–40 nm in thickness were deposited at 90–120°C onto water and chlorine treated, or, on carbon coated NaCl substrates. Tellurium was deposited at temperatures both below and above the monoclinic to FCC polymorphic phase transformation temperature ( T c=145°C) of Ag 2Te. The Ag–Te reaction occurred during the Te deposition. The samples were investigated by TEM, SAED and EDS: The Ag–Te compound developed at 200°C (above T c) exhibited large oriented crystals of mainly monoclinic phase regardless of the substrate. Films developed at 115°C (below T c) on the (0 0 1) Ag single crystal and on the randomly oriented Ag showed a monoclinic Ag 2Te phase of oriented mosaic crystals and of random polycrystalline Ag 2Te film, respectively. The influence of the polymorphic phase transition on the structure and morphology was revealed: As the random Ag–Te compound films passes T c on cooling, during a heating–cooling cycle, nucleation and growth of a textured large grain monoclinic Ag 2Te phase occurs attributed to the enthalpy difference of Δ H=0.17 kcal/mol and minimisation of surface energy.